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The coal-fired power plant fly ash (FA) and bottom ash (BA) are gradually used as alternative materials in the concrete. However, knowledge of the leaching characteristics of using both incinerator ashes in concrete production is lacking. This work aimed to evaluate the leaching behavior of the FA and BA used in concrete production by employing batch and tank leaching tests. The outcomes of both leaching tests showed that there was no considerable leaching of any trace elements to the environment, and it remains much lower than standard limitations for utilization as construction materials. The results of cumulative mass discharge showed that the slope of flux time for all elements was less than 0.4 and because of that, primary surface wash-off was the main discharge process of all the heavy metals. Strength test results revealed that there was not much difference between coal ash concrete (CAC) and the control mix at the initial age of curing time. Despite that, at a long period of curing time (180 days), the compressive strength of CAC containing 20% FA as cement replacement and 100% BA as fine aggregate replacement increased by 76% due to the pozzolanic reaction of BA and FA in comparison to the normal concrete, while, due to the high porosity of BA, the workability of CAC decreased by 50%. The outcomes of the current work revealed that the combined use of FA and BA can be counted as a promising alternative in the production of sustainable concrete for structural applications toward sustainable development. [ABSTRACT FROM AUTHOR]

A key goal of environmental policies and circular economy strategies in the construction sector is to convert demolition and industrial wastes into reusable materials. As an industrial by-product, Waste marble (WM), has the potential to replace cement and fine aggregate in concrete which helps with saving natural resources and reducing environmental harm. While many studies have so far investigated the effect of WM on compressive strength (CS), it is undeniable that conducting experimental activities requires time, money, and re-testing with changing materials and conditions. Hence, this study seeks to move from traditional experimental approaches towards artificial intelligence-driven approaches by developing three models—artificial neural network (ANN) and hybrid ANN with ant colony optimization (ACO) and biogeography-based optimization (BBO) to predict the CS of WM concrete. For this purpose, a comprehensive dataset including 1135 data records is employed from the literature. The models' performance is assessed using statistical metrics and error histograms, and a K-fold cross-validation analysis is applied to avoid overfitting problems, emphasize the models' reliable predictive capabilities, and generalize them. The statistical metrics indicated that the ANN-BBO model performed best with a correlation coefficient (R) of 0.9950 and root mean squared error (RMSE) of 1.2017 MPa. Besides, the error distribution results revealed that the ANN-BBO outperformed the ANN and ANN-ACO with a narrower range of errors so that 98% of the predicted data points in the training phase by the ANN-BBO model experienced errors in the range of [-10%, 10%], whereas for the ANN-ACO and ANN models, this percentage was 85% and 79%, respectively. Additionally, the study employed SHapley Additive exPlanations (SHAP) analysis to clarify the impact of input variables on prediction accuracy and found that the specimen's age is the most influential variable. Eventually, to validate the ANN-BBO, a comparison was performed with the results of previous studies' models. [ABSTRACT FROM AUTHOR]

The waste management sector is crucial for protecting the environment, conserving resources, and promoting sustainable development by ensuring efficient disposal, recycling, and minimizing the harmful impact of waste. This study aims to understand the performance levels (compressive strength), environmental impact, and overall sustainability of three concrete mixes, two of which use recycled materials. The mixes are defined as a conventional mix, mix one, which replaces dune sand for recycled rubber in the mix design, and mix two, which utilizes recycled aggregate as a replacement for fine aggregates. SEM-EDS is used to assess the elemental composition and surface morphology of the materials. The potential leaching of pollutants such as polycyclic aromatic hydrocarbons (PAHs), non-targeted organic compounds, and heavy metals was obtained using GC/MS and ICP-OES. The results showed low concentrations of PAHs in all mixes and a low calculated Potential Ecological Risk Index (PERI), where the conventional mix and mix two had the lowest risk (55 and 33, respectively) compared to mix one, which displayed a higher risk of 125. The results of the heavy metals assessment yielded that mix one was the most contaminated, with 1535 mg/kg of nickel and 1200 mg/kg of zinc, followed by the conventional mix, with 1385 mg/kg of nickel and 135.5 mg/kg of chromium, and finally, mix two was the least contaminated with 378.5 mg/kg of nickel and 142.5 mg/kg of zinc. Overall, the sustainability potential showed that mix two, with the recycled aggregates, was the most sustainable, with a Building Material Sustainability Potential (BMSP) value of 9.25. The study advocates for a shift toward sustainable concrete practices to mitigate environmental impacts while maintaining structural integrity. [ABSTRACT FROM AUTHOR]

Concrete, a widely used construction material, is under scrutiny due to its environmental impact, primarily stemming from cement production. Researchers are exploring alternative materials and mix designs to mitigate these effects. Supplementary cementitious materials (SCMs) like Ground Granulated Blast Furnace Slag (GGBS) show promise, reducing carbon emissions and enhancing concrete properties. Additionally, the extraction of natural aggregates poses environmental and health risks, necessitating the use of sustainable waste materials. Various wastes, including GGBS and clastic sand, are being investigated for their suitability in concrete production. This study aims to evaluate the performance of concrete incorporating GGBS and clastic sand (CLS) as substitutes. Understanding their impact on concrete properties will aid in developing more sustainable construction practices, contributing to reduced carbon emissions. Test results show mechanical property improvements with increasing GGBS and CLS content up to an optimal point, beyond which further enhancement ceases, likely due to unreacted materials acting as fillers. Using the response surface method, compressive strength values closely match experimental observations with a confidence level exceeding 95%. This research underscores the potential of GGBS and CLS in enhancing concrete sustainability and performance, crucial for environmentally responsible construction practices. [ABSTRACT FROM AUTHOR]

Utilization of recycled aggregates into concrete has taken a significant stride toward achieving sustainable construction, whereas temperature remains a pivotal factor adversely affecting the diverse concrete properties during service life. Thus, when exposed to elevated temperature, enhancing and evaluating sustainable concrete properties has become essential. The present article concentrates on the physical, destructive, and nondestructive properties of concrete, incorporated with fine recycled refractory brick (RRB) as a replacement of fine aggregate in combination with polypropylene fiber as the reinforcing agent, after exposure to elevated temperatures. To accomplish this, four distinct concrete blends have been prepared, with 10%, 20%, and 30% substitution of fine aggregate with RRB including one conventional (control) mix. Moreover, 1% polypropylene fiber has been incorporated as a reinforcing agent to meet the expected strength parameters. The concrete specimens have been exposed to different temperatures, 200°C, 400°C, 600°C, 800°C, 1,000°C, and 1,200°C. After exposure, different tests (visual appearance, mass loss, density loss, stress–strain profiles and compressive strength, ultrasonic pulse velocity, dynamic modulus of elasticity, degree of damage, failure pattern, and scanning electron microscope analysis) have been conducted to assess the diverse properties of concrete. The experimental findings have conclusively indicated optimal performance when 20% fine aggregate has been replaced with RRB with a compressive strength of 35.02 MPa at ambient temperature. Whereas, the specimen with 10% fine aggregate replacement with RRB has shown a compressive strength of 38.98 MPa at 400°C. All specimens, irrespective of the RRB replacement level, indicated excellent consistency of concrete with an ultrasonic pulse velocity value greater than 4.4 km/s up to 200°C, which was then followed by stepwise degradation with further temperature increases. In the authors' opinion, natural fine aggregate partially replaced with RRB in combination with polypropylene fiber holds promising potential for the manufacturing of sustainable concrete intended for use under elevated temperature. Practical Applications: The newly developed concrete blend, designed to be both sustainable and heat-resistant, will hold the promise of safeguarding natural resources and saving Mother Earth. By incorporating a particular alternative aggregate (recycled refractory brick), this innovation will not only curtail manufacturing expenses for heat-resistant concrete but also repurpose waste effectively. This sustainable heat-resistant concrete can be applied to concrete structures and members exposed to high temperatures, protecting them from rapid deterioration caused by repeated harsh conditions. Its implementation will not only enhance durability and efficiency of these structures but also lead to significant savings on maintenance costs, particularly in steel making industries. [ABSTRACT FROM AUTHOR]

It is widely accepted that cement and concrete are substantial sources of CO2 emissions. Researchers have been looking to replace cement with industrial waste to reduce the environmental impact of concrete production. The current research focuses on successfully using marble powder (M) and porcelain powder (P) instead of cement to produce cement mortar. Both mechanical and microstructural characteristics of several single and binary mixtures consisting of M and P were examined, with 13 mixes with M and P having been replaced by 2.5, 5, 7.5, and 10% of cement weight. For all mixtures in this work, compressive strength, flexural strength, SEM analysis, and thermogravimetric analysis (TG/DTA) were applied. The mixtures containing 10% M, 10% P, and 5% M+5% P demonstrated the best results. The maximum values recorded in compressive strength were 52, 55, and 50 MPa, whereas the control mix had 30 MPa. The maximum values for flexural strength were 9.24, 10.64, and 8.4 MPa in comparison with the 7 MPa of the control mix. Moreover, SEM analysis demonstrated the existence of a thick and compacted microstructure, which is predominantly the result of the formation of both Calcium Hydroxide (C-H) and high-density Calcium Silicate Hydrate (C-S-H) phases in all blends. SEM images demonstrated how hydration compounds formed and how the presence of M and P improved bonding. The difference in the quantities and types of phases distinguished by the different types of substitute material was also noted. The decrease in C-H, which is most prominent after a hydration period of 28 days, is primarily attributed to the interaction between C-H and M and P. Thus, this study demonstrates that M and P, by themselves or in combination, can be utilized as alternative resources in the production of high-performance and sustainable concretes. [ABSTRACT FROM AUTHOR]

Construction using eco-friendly materials reduces environmental impact and promotes sustainable practices. This research uses sawdust and steel fibers to design sustainable concrete. The main goal is to improve mechanical properties and reduce embodied carbon emissions. This study examines the mechanical properties of concrete with different sawdust and steel fiber combinations to fill a gap in the literature. In this research synergistic effect of saw dust and steel fiber on concrete characteristics have been studied. The research also examines these pairings' environmental benefits. This study used a response surface methodology (RSM) to design an experimental program and assess the effects of input variables (sawdust and steel fiber percentages) on output responses like compressive strength (CS), split tensile strength (STS), flexural strength (FS), modulus of elasticity (MOE), embodied carbon (EC), and eco-strength efficiency (ESE). Established testing methodologies and RSM provided an optimum prediction model based on specimen mechanical properties. Sawdust and steel fibers enhances concrete's mechanical properties. Varying proportions of both materials were added in mix; sawdust (0%-12%) and steel fiber (0%-2%). The experimental findings suggest that the optimized composition achieved the following mechanical properties: 13.85 MPa compressive strength, 1.4 MPa split tensile strength, 3.67 MPa flexural strength, 18.027 GPa modulus of elasticity, 211.272 kg CO2e/m3 embodied carbon, and 0.065487 eco-strength efficiency. This research showed that the aims of improving mechanical properties and reducing embodied carbon were achieved. As per multi-objective optimization, optimal percentages of saw dust and steel fibers in concrete are 11.81% and 0.063% respectively. The investigation yielded many suggestions. To test the optimal blend composition of ecologically friendly concrete in real-world building projects, start with realistic projects. Finally, life cycle evaluations and cost studies are needed to determine the environmental and economic impacts of eco-friendly concrete compared to standard options. [ABSTRACT FROM AUTHOR]

Considering the increasing need for optimal use of water resources, using types of waste water instead of part of the water for making concrete and also reducing the use of potable water in concrete is particularly important, especially in developing countries. Accordingly, this study aimed to investigate and reinforce using greywater as a potential alternative to mixing water in concrete. The specimens' fresh, hardened, and durable properties from 14 concrete mix designs containing six mixing water types, three natural zeolite levels (0, 10, and 20%), and two silica fume levels (0 and 8%) were tested to achieve that. Mixing waters in this study consisted of distilled water, raw greywater, diluted greywater (50% greywater, 50% distilled water), simulations of greywater's salt and organic pollutants, and synthetic greywater. The results showed that raw greywater reduced average compressive strength by 8%, while diluted greywater caused a 1.5% increase instead. Mixing water standards requirements were satisfied on both raw and diluted greywater cases. The results also showed that the impact of greywater on the durability properties of concrete was non-critical in most cases, while diluted greywater, even slightly (4%), improved bulk electrical resistance (RCPT). The test results of synthetic waters showed that reducing chemically active salts and/or organic pollution in greywater can effectively increase the performance of the produced concrete. Using 8% silica fume as cement replacement improved the compressive strength of greywater-made concrete by up to 16% and reduced the cracks and porosity of the specimens based on SEM images. On the other hand, using 20% natural zeolite as cement replacement increased surface (using Wenner probes) and bulk chloride ion penetration by 36 and 78%, respectively. Based on these results, silica fume and natural zeolite replacement are impressive tools to reinforce greywater-made green concrete so that it can properly rival and even replace regular concrete even when using more polluted greywater. Furthermore, these replacements can be great potential alternatives to wastewater dilution or treatments. [ABSTRACT FROM AUTHOR]

Concrete is the most commonly used construction material. However, its production leads to high carbon dioxide (CO2) emissions and energy consumption. Therefore, developing waste-substitutable concrete components is necessary. Improving the sustainability and greenness of concrete is the focus of this research. In this regard, 899 data points were collected from existing studies where cement, slag, fly ash, superplasticizer, coarse aggregate, and fine aggregate were considered potential influential factors. The complex relationship between influential factors and concrete compressive strength makes the prediction and estimation of compressive strength difficult. Instead of the traditional compressive strength test, this study combines five novel metaheuristic algorithms with extreme gradient boosting (XGB) to predict the compressive strength of green concrete based on fly ash and blast furnace slag. The intelligent prediction models were assessed using the root mean square error (RMSE), coefficient of determination (R2), mean absolute error (MAE), and variance accounted for (VAF). The results indicated that the squirrel search algorithm-extreme gradient boosting (SSA-XGB) yielded the best overall prediction performance with R2 values of 0.9930 and 0.9576, VAF values of 99.30 and 95.79, MAE values of 0.52 and 2.50, RMSE of 1.34 and 3.31 for the training and testing sets, respectively. The remaining five prediction methods yield promising results. Therefore, the developed hybrid XGB model can be introduced as an accurate and fast technique for the performance prediction of green concrete. Finally, the developed SSA-XGB considered the effects of all the input factors on the compressive strength. The ability of the model to predict the performance of concrete with unknown proportions can play a significant role in accelerating the development and application of sustainable concrete and furthering a sustainable economy. [ABSTRACT FROM AUTHOR]

Abstract A key goal of environmental policies and circular economy strategies in the construction sector is to convert demolition and industrial wastes into reusable materials. As an industrial by-product, Waste marble (WM), has the potential to replace cement and fine aggregate in concrete which helps with saving natural resources and reducing environmental harm. While many studies have so far investigated the effect of WM on compressive strength (CS), it is undeniable that conducting experimental activities requires time, money, and re-testing with changing materials and conditions. Hence, this study seeks to move from traditional experimental approaches towards artificial intelligence-driven approaches by developing three models—artificial neural network (ANN) and hybrid ANN with ant colony optimization (ACO) and biogeography-based optimization (BBO) to predict the CS of WM concrete. For this purpose, a comprehensive dataset including 1135 data records is employed from the literature. The models’ performance is assessed using statistical metrics and error histograms, and a K-fold cross-validation analysis is applied to avoid overfitting problems, emphasize the models’ reliable predictive capabilities, and generalize them. The statistical metrics indicated that the ANN-BBO model performed best with a correlation coefficient (R) of 0.9950 and root mean squared error (RMSE) of 1.2017 MPa. Besides, the error distribution results revealed that the ANN-BBO outperformed the ANN and ANN-ACO with a narrower range of errors so that 98% of the predicted data points in the training phase by the ANN-BBO model experienced errors in the range of [-10%, 10%], whereas for the ANN-ACO and ANN models, this percentage was 85% and 79%, respectively. Additionally, the study employed SHapley Additive exPlanations (SHAP) analysis to clarify the impact of input variables on prediction accuracy and found that the specimen’s age is the most influential variable. Eventually, to validate the ANN-BBO, a comparison was performed with the results of previous studies’ models.

Abstract Self-Compacting Concrete (SCC) allows for the use of non-desalted sea sand as a fine aggregate, but the durability of triple mix SCC with partial sea sand replacement remains unclear. To optimize binder and fine aggregate replacements, tests for consistency, setting times, soundness, compressive strength, and Ultrasonic Pulse Velocity were performed. Six SCC variations, incorporating 30 $$\%$$ % Class F Fly Ash (FA), 5 $$\%$$ % Ground Granulated Blast Furnace Slag (GGBS), and various fine aggregate combinations, were evaluated for their fresh, mechanical, microstructural, and durability properties. Results demonstrated that SCC with 50 $$\%$$ % sea sand and 50 $$\%$$ % manufactured sand achieved superior 90 $$^{th}$$ th day compressive strength. This improvement was attributed to accelerated cement setting and enhanced FA reactivity, leading to better hydration products. Microstructural analysis revealed more hydration products and fewer pores in specimens with 50 $$\%$$ % sea sand, due to the disconnected pore structure from Friedel’s salt formation. Chloride binding in concrete involves both chemical and physical mechanisms. Chemical binding is related to Friedel’s salt, while physical binding depends on Calcium-Silicate-Hydrate (C-S-H) content. Dense C-S-H formation from sea sand, confirmed by Scanning Electron Microscope (SEM) images, results in greater chloride binding. Additionally, aluminum oxide in FA and GGBS enhances chemical binding by forming Friedel’s salt.

Blast furnaces create iron and steel from pig iron, which in turn produces iron slag. Iron ore is the primary raw material for these transformations. Slag aggregate, a byproduct of the iron and steel industry, is a sustainable building material. In order to produce more environmentally friendly and cost-effective concrete, this study evaluated the effect of inclusion of two waste materials in concrete including, 10% treated cement kiln dust (TCKD) as cement weight replacement with different volumetric contents (15, 25, and 35%) of iron slag coarse aggregate (ISCA) as a replacement to natural coarse aggregate. Microstructure, static modulus of elasticity, splitting tensile strength, flexural strength, water absorption, and workability were among the many concrete qualities studied. There was an improvement in oven-dry, splitting tensile, flexural, compressive, ultrasonic pulse velocity, and static modulus of elasticity as ISCA content rose, as shown in the results. Increasing the ISCA concentration reduces thermal conductivity. Depending of the ISCA content, increasing the compressive strength by 1.43–12.4% and the splitting tensile strength by 0.4–5.34% were both possible. There was an additional increase of 1.3–9.15% in flexural strength. From the experimental results, it can be observed that innovative and potent method for producing structural sustainable concrete is provided in this study by inclusion of two waste materials, including TCKD and ISCA. The sustainable concrete produced has high strength and low thermal conductivity relative to concrete not containing these waste materials, which can be used in different construction projects. Moreover, the use of these waste materials in concrete has a benefit of reducing the environmental pollution. All the above-mentioned results conforms the goal of this study.

This study aims to serve as a performance indicator for the workability and strength of concrete when coarse aggregate, sand, cement, and water are partially substituted with waste plastic bottle caps. The significance of these alternative plastic water bottle caps is to reduce plastic trash that is difficult to lapse and to prevent waste that can be transformed to something that may be employed in the advancement of technology in the future. The principle of "Reduce, Reuse, and Recycle" is used, which not only lowers environmental pollution but also reduces costs. In the building industry, concrete is the most often utilized material. In order to preserve natural resources and minimize the number of materials that end up in landfills, green construction is becoming a more significant worldwide issue. Empty cans and bottle tops from drinking water bottle produce a lot of garbage. The difficulty of biodegrading plastic trash and the need for techniques for recycling or reuse make this a problem for the environment. Such problems are being investigated in this study in order to determine whether it could be possible to partially replace coarse aggregate with 0, 6 and 12% in the manufacturing of concrete using discarded bottle caps. To evaluate the compressive strength, split tensile, and flexural strength test characteristics in a laboratory setting; waste bottle caps were used as replacements for coarse aggregate at different percentages. The highest compressive strength was determined to be 28.80 MPa with 12% replacement of used plastic bottle caps with a water cement ratio of 0.55. Advanced statistical methods, including RSM-CCD (Response Surface Method-Central Composite Design) and machine learning models ANN-LM (Artificial Neural Network- Levenberg Marquardt), were applied in this study to predict concrete performances based on mix design variations. It was found that ANN-LM model displayed more accurate prediction relative to RSM-CCD method. [ABSTRACT FROM AUTHOR]

Due to sustainability goals, there is an increasing need to recycle waste. In this concrete study, waste from the concrete production industry - concrete slurry, and glass industry waste were used. The concrete slurry was obtained by washing equipment in the concrete industry. The glass processing waste was obtained from technical water. The wet concrete slurry was used to replace the amount of water, the dry concrete slurry was used to replace the amount of fine aggregate, and the glass processing waste was used to replace the amount of cement from 5 % to 30 %. Thus, cement, sand, gravel, a superplasticiser, a crystallising admixture, and an air-entraining admixture were used in the concrete composition. In all the compositions, the same w/c ratio was maintained. For the fresh concrete mix, the density, air content, and hydration heat release were determined. For the hardened specimens, the speed of the ultrasound pulse propagation, density, compressive strength, water absorption, microstructure, and porosity parameters were determined. The determined mechanical properties indicate that replacing up to 20% of cement with glass processing waste improves the results.

Worldwide, annual glass waste production surpasses 200 million tonnes, urging exploration of sustainable reuse avenues. This study evaluates the incorporation of waste glass powder (WGP) into concrete as a partial replacement for fine aggregate. Thirty concrete mixes, varying water-cement ratios and WGP levels, underwent comprehensive analysis. Findings reveal that as WGP percentage in sand increases, the slump of concrete rises marginally until reaching maximum glass powder replacement, with workability remaining within the 50 to 100 mm range. At a 10% replacement level, early and later age strength minimally impacts compressive strength. WGP's workability and strength hinge on particle geometry, indicating increased concrete strength when mixed with WGP featuring higher surface area and improved cement paste bonding. To enhance solid waste management, conserve sand, and bolster sustainability, WGP can replace up to 10% of sand weight in concrete at lower water-cement ratios. Positive correlation exists between slump and WGP percentage replaced. Both water-cement ratio and replacement amount significantly influence compressive strength, as confirmed by ANOVA. However, long-term mechanical strength and durability research is essential before recommending WGP for environmentally friendly and sustainable concrete applications, promising increased understanding through additional data collection and analysis.

Due to rising living standards and population growth, saving fresh water will be a significant problem for the next generation. The Government is indirectly impacted by a significant financial burden due to the current usage of treated wastewater, in all of Egypt’s districts. As a case study, Egypt’s new administrative capital was chosen, given that it is today one of the most important cities and that its planning was predicated on making it a smart, sustainable city. The goal of the study was to develop methods for replacing potable water in the manufacture of concrete with tertiary-treated wastewater; however, used for concrete mixing or curing after concrete hardening. Property assessments of the fresh and hardened concrete were conducted, to ascertain the best water quality that can be used without compromising the quality or durability of the concrete. ; The results of this paper will serve as a guide for decision-makers looking to decrease costs and increase sustainability by using treated wastewater in making sustainable concrete for buildings, especially in recent decades, rising construction material usage has generated considerable environmental difficulties, particularly in the production of Ordinary Portland cement (OPC). [ABSTRACT FROM AUTHOR]

Structural characteristics of concrete incorporating Colloidal Nanosilica (CNS), Metakaolin (MK) and Alccofine (AF) were comparatively studied using X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Field Emission Scanning Electron Microscope (FESEM), and Fourier Transform Infrared spectroscopy (FTIR). The plasticizer demand and compressive strength at 3,7,28 and 90 days of curing ages were also determined. The results indicated that the demand for plasticizer content increased with CNS and MK incorporation owing to their large surface area and rough surface texture, respectively. However, AF decreased the plasticizer demand due to glassy surface morphology. Also, the compressive strength increased with replacement ratio. The tetranary blended systems (M6) proved to be more advantageous compared to binary, ternary and normal OPC systems. FTIR, TGA, XRD and FESEM analysis were consistent with the results of compressive strength. The improvement in properties of concrete at early ages was attributed to filler and nucleation effect of CNS and AF. At later ages, CNS modified the CSH by increasing the length of silicate chains, AF and MK diminished the portlandite content by utilizing it in pozzolanic reaction and filling of pores partially or completely especially by secondary CSH gel, led to denser structure. [ABSTRACT FROM AUTHOR]

The goal of this study was to produce sustainable concrete by reducing reliance on cement, which contributes to high carbon footprints, and natural sand, which is being depleted. Sugarcane bagasse ash (SCBA) was used to partially replace cement at 5 %, 10 %, and 15 %, while recycled polyethylene terephthalate (RPET) was used to partially replace sand at 5 %, 10 %, 15 %, and 20 %. The effects of these substitutions on concrete's mechanical and physical properties were examined after 28 days of water curing. The study observed a decrease in fresh density by 0.36 %–2.67 % with SCBA and RPET inclusion. The slump values ranged between 93 mm and 140 mm, indicating good workability. The reference concrete's compressive strength was 39.65 MPa, while the mix with 5 % SCBA and 10 % RPET achieved 38.23 MPa. This mix also showed a 1.2 % higher split tensile strength than the reference concrete. Although the reference concrete's flexural strength was the highest at 4.56 MPa, all SCBA-RPET mixes remained within 86 % of this value. All modified mixes weighed less than the reference concrete, with the compressive strength-to-weight ratio of the mix with 5 % SCBA and 10 % RPET being closest to the reference mix with only a 2.44 % reduction. These findings suggest that SCBA and RPET can be effectively used to produce sustainable concrete with comparable mechanical properties to conventional concrete.

Construction using eco-friendly materials reduces environmental impact and promotes sustainable practices. This research uses sawdust and steel fibers to design sustainable concrete. The main goal is to improve mechanical properties and reduce embodied carbon emissions. This study examines the mechanical properties of concrete with different sawdust and steel fiber combinations to fill a gap in the literature. In this research synergistic effect of saw dust and steel fiber on concrete characteristics have been studied. The research also examines these pairings’ environmental benefits. This study used a response surface methodology (RSM) to design an experimental program and assess the effects of input variables (sawdust and steel fiber percentages) on output responses like compressive strength (CS), split tensile strength (STS), flexural strength (FS), modulus of elasticity (MOE), embodied carbon (EC), and eco-strength efficiency (ESE). Established testing methodologies and RSM provided an optimum prediction model based on specimen mechanical properties. Sawdust and steel fibers enhances concrete’s mechanical properties. Varying proportions of both materials were added in mix; sawdust (0%–12%) and steel fiber (0%–2%). The experimental findings suggest that the optimized composition achieved the following mechanical properties: 13.85 MPa compressive strength, 1.4 MPa split tensile strength, 3.67 MPa flexural strength, 18.027 GPa modulus of elasticity, 211.272 kg CO2e/m3 embodied carbon, and 0.065487 eco-strength efficiency. This research showed that the aims of improving mechanical properties and reducing embodied carbon were achieved. As per multi-objective optimization, optimal percentages of saw dust and steel fibers in concrete are 11.81% and 0.063% respectively. The investigation yielded many suggestions. To test the optimal blend composition of ecologically friendly concrete in real-world building projects, start with realistic projects. Finally, life cycle evaluations and cost studies are needed to determine the environmental and economic impacts of eco-friendly concrete compared to standard options.

Abstract One of the major challenges in the civil engineering sector is the durability of reinforced concrete structures against carbonation during the physico-chemical process of interaction of hydrated cementitious composites with carbon dioxide. This aggressive process causes carbon penetration into the reinforcement part, which affects the behavior of the structure during its lifetime due to corrosion risk. A countermeasure is using alternative cementitious materials to improve concrete texture and resist increased carbonation depth (CD). Considering that the CD test requires a long time and a skilled technician, this study strives to provide an alternative approach by moving from traditional laboratory-based methods towards artificial intelligence (AI) techniques for modeling the CD of sustainable concrete containing fly ash (CCFA). Despite the development of single AI models so far, it is undeniable that utilizing metaheuristic optimization techniques in the form of hybrid models can improve their performance. To this end, a new hybrid model from the integration of biogeography-based optimization (BBO) technique with artificial neural network (ANN) is developed for the first time to estimate the CD of CCFA. The error distribution results revealed that 59% of the ANN predictions had errors within the range of (− 1 mm, 1 mm], while the corresponding percentage for the ANN-BBO predictions was 70%, indicating an 11% reduction in the prediction errors by the proposed hybrid model. Furthermore, A10-index highlighted a performance improvement of 78% for the hybrid model, which met the closeness of the predicted values to the observed ones, so that the value of this index for models of ANN and ANN-BBO was 0.5019 and 0.8947, respectively. Analyzing the cross-validation confirmed the reliability and generalizability of the developed model. Also, the three most influential variables in estimating the CD were exposure time (27%), carbon dioxide concentration (22%), and water/binder (18%), respectively. Finally, the superiority of the ANN-BBO model was verified by comparing it with previous studies’ models.

Geopolymer concrete (GC) emerges as a sustainable alternative yet faces challenges in achieving optimal resource utilization for strength development. Balancing these aspects is crucial for its large-scale adoption as a sustainable material. The type and dosage of precursors, activator, curing, and mixing conditions influence compressive strength, setting time, and workability. Moreover, multiple experimental trials are required for a desirable geopolymer blend. Even the experimental parameters alone do not meet the design principles concerning sustainable construction. This paper presents a study on the mix design and interpretation of machine learning techniques (MLT) with XAI. To train the model, extensive experimental databases using the shapley additive explanations (SHAP) technique rank input factors that impact the strength aspect. The prediction models' performance was compared using coefficient of determination (R2) and root mean square error (RMSE). SHAP interpretations reveal that temperature, Na to Al ratio, and NaOH molarity are the main factors influencing the compressive strength of GC. Further, these parameters were crucial in developing the dense geopolymer matrix. By integrating XAI into the MLT approach, we have also opened new criteria for understanding the complex relationships between geopolymer concrete potential parameters and their compressive strength.

While several studies have assessed the applicability of using biochar in cement mortar and concrete preparation based on the best mechanical properties, this evaluation method should be improved to consider the techno-economic feasibility and the environmental impacts. To address this research gap, this study attempts to compare between the conventional concrete with 100 % cement as a control mixture (CM) and dumping of sludge into open sites (scenario_1), and biochar concrete using alum sludge biochar (ASB) as a partial cement replacement (scenario_2), regarding the project life cycle assessment (LCA) and economic feasibility. A multi-criteria decision-making (MCDM) framework was used to assign scores to the environmental LCA criteria, material functional performance tests, and cost considerations. The two scenarios were arranged in SimaPro LCA software, and then the different criteria were analyzed using the TOPSIS technique to choose the best alternative. The study demonstrated that the functional properties of the cement mixture containing 5 % of ASB were almost comparable to those of CM, owing to the presence of significant amounts of quartz (SiO2) that bonded strongly with cement molecules. This ASB mixture also enjoyed the least environmental impacts, reducing the global warming potential (GWP) by 32.2 % compared with the CM scenario. The scores of the “Cost” criterion, considering the price of raw materials, energy, production, and maintenance, for the two alternatives were almost comparable, depicting that scenario_2 achieved the highest closeness coefficient of 0.95 in the MCDM overall scoring. This study concluded that biochar could be incorporated into cementitious mixtures due to its lower impact on global warming to maintain a sustainable and economic concrete industrial strategy. Future studies should focus on studying the long-term durability of the biochar-based concrete mixtures and integrating into the MCDM strategy; in addition, determining the correlation between sustainable construction implementation and sustainable development goals achieved.

As the global concrete industry shifts towards sustainable practices, there is an increasing focus on mitigating the environmental impacts of ordinary Portland cement (OPC)-based concrete, which is notorious for its significant greenhouse gas emissions, high energy consumption, and substantial demand for natural resources. This urgency is compounded by the growing production of waste tile ceramic materials due to rapid urban development, leading to enhanced research into their recyclability within concrete for improved durability and sustainability. This study explores the development of high-strength concrete utilizing waste tile ceramic aggregates (WTCAs) and waste tile ceramic powder (WTCP) as replacements for natural aggregate and OPC, respectively. To further enhance the concrete's mechanical properties and microstructure, silica nanoparticles derived from waste bottle glass (WBGNPs) were integrated in varying proportions ranging from 2 % to 10 % of the binder content. Optimal results were achieved with a full replacement of natural aggregate by WTCAs, 60 % substitution of OPC by WTCP, and the inclusion of 4 % WBGNPs, which collectively exhibited superior compressive, splitting tensile, and flexural strengths. Microstructural analyses revealed that the addition of WBGNPs improved the hydration process, increased gel density, and reduced porosity. From the obtained numerical results, the coefficient of determination value of 0.92 further confirms the model's predictive strength, demonstrating that the Random Forest algorithm can reliably estimate the compressive strength. The findings indicate that the concrete formulated with WTCP and WBGNPs not only meets diverse construction demands but also significantly contributes to environmental sustainability by reducing impacts on global warming and minimizing landfill usage. This study advocates for the strategic incorporation of WTCP and WBGNPs in concrete applications to promote environmentally sustainable construction practices. It is highly recommended that WTCP be utilized in sustainable binders as a replacement for OPC and natural aggregates to enhance it strength and durable properties, reduce the environmental issues, costs, and the depletion of natural resources.

One of the major challenges in the civil engineering sector is the durability of reinforced concrete structures against carbonation during the physico-chemical process of interaction of hydrated cementitious composites with carbon dioxide. This aggressive process causes carbon penetration into the reinforcement part, which affects the behavior of the structure during its lifetime due to corrosion risk. A countermeasure is using alternative cementitious materials to improve concrete texture and resist increased carbonation depth (CD). Considering that the CD test requires a long time and a skilled technician, this study strives to provide an alternative approach by moving from traditional laboratory-based methods towards artificial intelligence (AI) techniques for modeling the CD of sustainable concrete containing fly ash (CCFA). Despite the development of single AI models so far, it is undeniable that utilizing metaheuristic optimization techniques in the form of hybrid models can improve their performance. To this end, a new hybrid model from the integration of biogeography-based optimization (BBO) technique with artificial neural network (ANN) is developed for the first time to estimate the CD of CCFA. The error distribution results revealed that 59% of the ANN predictions had errors within the range of (− 1 mm, 1 mm], while the corresponding percentage for the ANN-BBO predictions was 70%, indicating an 11% reduction in the prediction errors by the proposed hybrid model. Furthermore, A10-index highlighted a performance improvement of 78% for the hybrid model, which met the closeness of the predicted values to the observed ones, so that the value of this index for models of ANN and ANN-BBO was 0.5019 and 0.8947, respectively. Analyzing the cross-validation confirmed the reliability and generalizability of the developed model. Also, the three most influential variables in estimating the CD were exposure time (27%), carbon dioxide concentration (22%), and water/binder (18%), respectively. Finally, the superiority of the ANN-BBO model was verified by comparing it with previous studies' models. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the environmental impact of using red mud (RM) as a partial replacement for cement in concrete production. Using industrial byproducts such as red mud as a raw material in concrete can reduce the environmental impacts of concrete and alumina industries. Red mud can also provide a sustainable solution for its disposal problem, while also improving the durability and strength of concrete. Life cycle assessment methodology was applied using Simapro© software. A cradle-to-gate analysis was carried out. The results were analyzed based on the Ecoinvent 3.8 database and ReCiPe method for 18 impact categories. The results show that the use of RM in concrete production also had a significant positive impact on all environmental impact categories, including freshwater ecotoxicity and human carcinogenic toxicity, compared to traditional concrete production. On the other hand, disposing of RM in landfills had been analyzed and from the results RM disposal showed significant negative impacts on the environment, including human carcinogenic toxicity, freshwater eutrophication, and marine ecotoxicity. These reductions vary between 0.2% (water consumption category) and 939.7% (Human carcinogenic toxicity). This study presents a significant contribution to the aluminum and construction industries by shedding light on the possibility of utilizing RM as a sustainable raw material in concrete production, leading to a reduction in environmental impact. By analyzing the properties of various concrete samples containing different percentages of RM, this study also highlights the potential for enhancing the mechanical properties of concrete through the incorporation of RM in certain amounts. [ABSTRACT FROM AUTHOR]

This research paper explained in detail how well regular concrete works and how well concrete with fly ash and ground granulated blast furnace slag (GGBS) performs as a substitute for cement. Through a series of experiments, the objective of the study was to perform an experiment that promotes the usage of partial replacement-based concrete which can replace the conventional concrete as well as contributes to sustainable development. A dedicated methodology was developed for the study, focusing on the mechanical and durability properties of the materials with inducing sustainable materials. The methodology study examined the mechanical properties, durability, and microstructural attributes of concrete blends. Cement concrete specimens with binder ratios (%) of 0.3, 0.4, and 0.5 were tested for compressive strength, rapid chloride permeability, SEM, and XRD at 28, 56, and 90 days. Fly ash and GGBS were used to partially replace cement at 0% to 70% for all binder ratios by weight of cement. There were optimal replacement percentages for each binder ratio and fly ash; the concrete partially substituted with GGBS had similar or enhanced mechanical properties to conventional concrete. The novelty of the study is to incorporate microstructure analysis for the same samples that shall enable analysing the behaviour of the partial replaced materials with conventional concrete. In connection with the results, the study had found lower RCPT values in partial replacement concrete specimens, fly ash and GGBS increased chloride ion resistance. SEM and XRD analyses revealed the microstructural properties and phase composition of concrete mixtures, showing how supplementary cementitious materials refine pore structure and provide durable hydration products. This study shows that fly ash and GGBS can improve concrete performance as well as reduce impact on environment and applications in construction. [ABSTRACT FROM AUTHOR]